/**
 * This class is used to calculates the distance between two points (given the     
 *  latitude/longitude of those points).
 */

/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/
/*::                                                                         :*/
/*::  This routine calculates the distance between two points (given the     :*/
/*::  latitude/longitude of those points). It is being used to calculate     :*/
/*::  the distance between two ZIP Codes or Postal Codes using our           :*/
/*::  ZIPCodeWorld(TM) and PostalCodeWorld(TM) products.                     :*/
/*::                                                                         :*/
/*::  Definitions:                                                           :*/
/*::    South latitudes are negative, east longitudes are positive           :*/
/*::                                                                         :*/
/*::  Passed to function:                                                    :*/
/*::    lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees)  :*/
/*::    lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees)  :*/
/*::    unit = the unit you desire for results                               :*/
/*::           where: 'M' is statute miles                                   :*/
/*::                  'K' is kilometers (default)                            :*/
/*::                  'N' is nautical miles                                  :*/
/*::                                                                         :*/
/*::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::*/

package com.pi.util;

/**
 * @author Coy.Qiu
 *
 */
public class DistanceConverter {
	
	public double distance(double lat1, double lon1, double lat2, double lon2,
			String unit) {
		double theta = lon1 - lon2;
		double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2))
				+ Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2))
				* Math.cos(deg2rad(theta));
		dist = Math.acos(dist);
		dist = rad2deg(dist);
		dist = dist * 60 * 1.1515;
		if (unit.equalsIgnoreCase("K")) {
			dist = dist * 1.609344;
		} else if (unit.equalsIgnoreCase("N")) {
			dist = dist * 0.8684;
		}
		return (dist);
	}

	/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
	/* :: This function converts decimal degrees to radians : */
	/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
	private double deg2rad(double deg) {
		return (deg * Math.PI / 180.0);
	}

	/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
	/* :: This function converts radians to decimal degrees : */
	/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
	private double rad2deg(double rad) {
		return (rad * 180.0 / Math.PI);
	}


}
